Barnacles and marine growth on the hulls of ships, below the water line, are a significant factor in reducing the efficiency of marine shipping. There are two methods by which this problem has been addressed. The first has been the development of various anti-fouling paints. In general these paints include the composition tributyltin (TBT). For example, the most commonly used anti-fouling paint systems currently in use are the TBT-self-polishing copolymer (SPC) systems. TBT is toxic to marine life and also to humans. TBT can enter the environment in significant concentrations where ships sit in shallow relatively stationary water, and also as a result of ship hull cleaning. Thus, the use of TBT-containing paints is on the decline. Indeed, a number of countries have now banned the use of paints including TBT, or are in the process of passing legislation to prohibit its use. Alternative, non-TBT containing antifouling paints are being developed and tested but these tend to be effective for a shorter period and/or may be effective only against marine growth of selected types.
The second option for dealing with barnacles and marine growth is to conduct regular cleaning of ship hulls. Traditionally, ship hulls have been cleaned by divers operating small submarine machinery with steel brushes to brush off the barnacles and marine growth. However, this is a very time consuming process, the efficiency of the cleaning is questionable and the debris, which generally includes some possibly toxic paint, is discarded on the seabed at the mooring site of the ship (usually in a port).
Thus, it is an object of the present invention to provide a method and apparatus for cleaning the hull of a ship which reduces or overcomes the abovementioned problems, or which at least provides the public with a useful alternative.
Other objects of the invention may become apparent from the following description which is given by way of example only.